1. Technical Field
The present invention relates to a method and an apparatus for forming a beam. More particularly, the present invention relates to a method and an apparatus for forming an optimal beam with high accuracy.
2. Description of the Related Art
In a mobile communication system, the user capacity of the system is inversely proportional to the amount of interference caused by undesired users. Therefore, the undesired users must be excluded from the mobile communication system. To this end, an apparatus may be introduced to form an optimal beam directed toward a desired user or terminal. A beam forming apparatus, for example, equipped in a base station, receives multiple signals that are transmitted from many terminals and/or other base stations. Therefore, the beam forming apparatus needs to select a signal that is transmitted from a terminal of the desired user among the received multiple signals.
One beam forming apparatus calculates weight vectors for forming the optimal beam using data included in the received signals. However, in general the base station cannot obtain correct information concerning data streams included in the data signals. Therefore, the calculated weight vectors cannot achieve a high accuracy. Thus, a need exists for a beam forming apparatus capable of forming the optimal beam with accuracy.
Accordingly, it would be desirable to provide a method and an apparatus for forming an optimal beam with high accuracy.
In accordance with one aspect of the present invention, there is provided a method of forming a beam. In the method, data signals and pilot signals are generated by despreading received signals at a plurality of antennas. Each of the received signals includes a modulated data signal and a modulated pilot signal. A first covariance matrix for the pilot signals is calculated. A second covariance matrix is calculated for averages of the pilot signals. A weight vector is calculated based on the first and second covariance matrices. A beam forming output signal for forming a beam is generated based on the data signals and the weight vector.
In accordance with another aspect of the present invention, there is provided an apparatus for forming a beam. The apparatus comprises a despreading unit configured to generate a plurality of data signals and a plurality of pilot signals by despreading a plurality of received signals, wherein each of the received signals includes a modulated data signal and a modulated pilot signal; a weight calculator configured to calculate a first covariance matrix for the pilot signals, to calculate a second covariance matrix for averages of the pilot signals, and to calculate a weight vector based on the first and second covariance matrices; and a beam forming unit configured to generate a beam forming output signal based on the data signals and the weight vector.
In accordance with still another aspect of the present invention, there is provided an apparatus for forming a beam. The apparatus comprises a despreading unit configured to generate a plurality of data signals and a plurality of pilot signals by despreading a plurality of received signals, each of the received signals including a modulated data signal and a modulated pilot signal; a weight calculator configured to calculate a first covariance matrix for the demodulated pilot signals, to calculate a second covariance matrix for averages of the respective pilot signals, and to calculate a weight vector using the first and second covariance matrices; and a beam forming unit configured to generate a beam forming output signal using the data signals and the weight vector.
In accordance with still another aspect of the present invention, there is provided a communication system including an apparatus for forming a beam. The system comprises a plurality of terminals configured to modulate data signals and pilot signals to generate transmitted signals including a modulated data signal and a modulated pilot signal; and a base station configured to generate a beam forming output signal. Beneficially, the base station comprises a plurality of antennas for receiving the transmitted signals; a despreading unit configured to generate a plurality of despread data signals and a plurality of despread pilot signals by despreading the received signals; a weight calculator configured to calculate a first covariance matrix for the despread pilot signals, to calculate a second covariance matrix for averages of the despread pilot signals, and to calculate a weight vector using the first and second covariance matrices; and a beam forming unit configured to generate the beam forming output signal for forming the beam using the despread data signals and the despread weight vector.
In accordance with still another aspect of the present invention, there is provided a communication system including an apparatus for forming a beam. The system comprises a plurality of base stations configured to modulate data signals and pilot signals to generate signals including a modulated data signal and a modulated pilot signal; and a terminal configured to generate a beam forming output signal. The terminal may comprise an antenna for receiving the received signals; a despreading unit configured to generate a plurality of despread data signals and a plurality of despread pilot signals by despreading the received signals; a weight calculator configured to calculate a first covariance matrix for the modulated pilot signals, to calculate a second covariance matrix for averages of the despread pilot signals, and to calculate a weight vector using the first and second covariance matrices; and a beam forming unit configured to generate the beam forming output signal for forming the beam using the despread data signals and the despread weight vector.